The present invention pertains to a pushbutton-actuated counting selector switch which provides an ordered set of n outputs, the next sequential output being selected and visually identified each time the pushbutton is actuated, the sequence of outputs being repeated after n sequential pushbutton actuations.
In the prior art, various approaches have been used to detect that a counter has reached a certain value and then reset the counter to some new value. Thus, in U.S. Pat. No. 3,962,565, issued June 8, 1976 to Bao-Dam N. Guyen-Phuoc, an apparatus is provided which automatically presets an electric pulse counter to a predetermined initial count. The apparatus includes a pulse generator which is connected during a preset operation to the count input of the counter through an electronic gate. The electronic gate, in response to an auxiliary circuit detecting an overflow at the output of the pulse counter, actuates the pulse generator, which increments the pulse counter until the desired preset value is obtained. The above described technique, although quite useful when working at high frequencies, for example over 100 MHz., is also quite costly and complex when such high frequency operation is not required.
In U.S. Pat. No. 4,150,337 issued Apr. 17, 1979, an up-down counter output is prevented from overflowing or underflowing by stopping it when all of the counter output digits are at the same one of a plurality of possible logic levels. The detection of such a condition is accomplished by comparing the logic value of each of the digits with the logic value of at least one other digit and providing a stop signal when all the comparisons are equal. The above described technique suffers from the fact that it requires a relatively large amount of logic to implement and further from the fact that it is limited to detecting only the maximum count possible for the counter being utilized.
In pending U.S. patent application Ser. No. 229,551, a selector switch is disclosed which simulates an n-position rotary-type switch. The selector switch makes use of a shift register and a counter, each of which is clocked when a pushbutton input is actuated. The shift register data output actuates the selected position indicator, while the data output from the counter provides a binary count corresponding to the selected switch position. Logic circuitry coupled to the output of the shift register and counter test for the selection of the highest numerical switch position and in response to such condition, enable both the shift register and counter to read in new data on the next actuation of the pushbutton input. The new data loaded on the next pushbutton actuation results in the data output of the selector switch corresponding to the first selected switch position, thus simulating a complete rotation of a rotary type switch.
It is a general object of the present invention to provide an improved rotary-type switch simulator.
It is another object of the present invention to provide an improved rotary-switch simulator which requires less logic to implement than prior art rotary-switch simulators.
These and other objects, features and advantages of the present invention will become more apparent from the detailed description of the preferred embodiment when read in conjunction with the drawing.